In a packaging system known from German published Gebauchsmuster No. 71 19 166, two pressurized containers or chambers are combined into a single unit, and these containers have valves which are operated simultaneously. The components contained in the respective containers are mixed together in a separate space or chamber upon the opening of the valves. Thus, the mixing process necessary before use takes place outside the chambers initially holding the components. Such an arrangement is also typical of other two-component packaging systems, such as the one described in German published patent application (DE-OS) No. 19 42 570. In each of these systems a separate mixing chamber is needed, and both chambers initially holding the components must be able to withstand the constant pressure of the propellants and any corrosion that may result from use of such propellants.
Another pressurized container assembly having two pressurized containers is described in U.S. Pat. No. 3,181,737 for dispensing liquids which are mixed together only when the liquids are to be discharged. More specifically, the patent provides a two-part dispenser comprising a first can or container having a first fluent material under atmospheric pressure, a second can or container having a second fluent material under pressure of a gas propellant, and means for coupling the cans together so that a valve of the second can is actuated to discharge the gas propellant and the second fluent material into the first can, the first can having a valve for discharging the mixture of fluents under pressure of the gas propellant.
Also, previously known is U.S. Pat. No. 3,451,593 which discloses a pressurized device for discharging a self-heating cosmetic preparation formed from two or more chemicals adapted to react exothermically and maintained in separate pressurized containers. The chemicals are stored in two separate containers, which each empty into a mixing chamber. There is no mixing of the total liquid contents of both containers in one of the containers. In fact, there is such a short time available for mixing that sufficient homogenization of the product to be dispensed cannot be assured.
U.S. Pat. No. 4,202,470 discloses a reusable two-chamber container assembly wherein one container propellant is contained in a sealed, flexible compartment positioned within the container as a mixture of gas and liquid under pressure in equilibrium at the temperature of the container.
All the internal protective lacquers and other chamber coatings which have hitherto been used have proved unstable to certain substances, for example hydrogen peroxide (H.sub.2 O.sub.2), in the event of long-term storage. Accordingly, attempts have been made to prevent corrosion completely by a pressure pack system adapted to meet the requirements of aerosol packaging; i.e., by using a two-chamber pressure pack. Two-chamber or pressure pack systems of the type in question are described, for example, in "Aerosol Report", Vol. 20, No. 5/81, 170-175 and Vol. 21, No. 4/82, 172-182 and also in "Seifen-Oele-Fette-Wachse", Vol. 108, No. 13/1982, 399/400.
A two-chamber pressure pack or aerosol can of this type is disclosed in U.S. Pat. No. 4,032,064 which discloses a normal opening for the associated valve and an approximately 3 mm wide bottom opening designed to be closed by a rubber plug. The feature of this prior art two-chamber system which is of importance in the present connection is an inner bag of plastic which may be polyethylene, polypropylene, a metallic foil laminate, etc., and which, in the region of the valve opening, comprises an outwardly tucked edge which, after fitting, rests on the rolled edge of the can. The disclosed inner bag has preformed folding lines which provide for controlled folding and hence for complete emptying of the bag, on release of the product. In addition, the valve seat contains a butadiene rubber seal. Ideally, the inner bag is gripped between the seal and the rolled edge of the can after the valve has been clinched on.
This prior art inner bag fills only about two-thirds of the can volume and contains all the active substance. The remaining volume of the can is filled with propellant gas through the bottom opening, for example by means of an injector needle. The propellant gas does not come into contact with the active substance even during evacuation and, after emptying, is destroyed together with the can.